According to E. Kamandi et al., Arch. Pharmaz., 307, 871-878 (1974), it is known to prepare threo-.beta.-phenylisoserine by the action of ammonia on an ester of cis-.beta.-phenylglycidic acid, followed by the action of barytes, in order to avoid racemisation, on the .beta.-phenylisoserine amide obtained as an intermediate.
According to E. Kamandi et al., Arch. Pharmaz., 308, 135-141 (1975), the action of benzylamine on an ester of trans-.beta.-phenylglycidic acid leads to the formation of erythro-N,N'-dibenzyl-.beta.-phenylisoserine amide which, on hydrogenation in the presence of palladium on charcoal, leads to erythro-.beta.-phenylisoserine-N-benzylamide.